Analytical methods have been developed for separation, quantitation and characterization of elements (principally metals) and their complex species (coordination compounds) present in biological samples at trace levels. In vivo and in vitro studies designed to produce biologically relevant results require the ability to separate and quantitate the metals in the low concentrations obtaining as well as the ability to relate their concentrations to the biological milieux and their components quantitatively. To understand the mechanisms of action of the drugs under study it is important to understand the interactions of the metal complexes with proteins and other constituents. Unfortunately many studies reported in the literature have been conducted at much higher concentrations for want of analytical methods with the requisite sensitivity. In the case of the platinum drugs there is a further complicating factor in the relatively slow kinetics of some of the reactions; many published studies assume that the metal complex species and their interconversions are.